cis-k8s-v1110-1-2-25

name	cis-k8s-v1110-1.2.25
description	Ensure that the --client-ca-file argument is set as appropriate (Automated)
category	cis-k8s
version	1.11.0
author	cyberstrike-official
tags	["cis","kubernetes","control-plane","api-server","client-ca-file","tls","client-certificate-authentication"]
cis_id	1.2.25
cis_benchmark	CIS Kubernetes Benchmark v1.11.0
tech_stack	["kubernetes"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

1.2.25 Ensure that the --client-ca-file argument is set as appropriate (Automated)

Profile Applicability

• Level 1 - Master Node

Description

Setup TLS connection on the API server.

Rationale

API server communication contains sensitive parameters that should remain encrypted in transit. Configure the API server to serve only HTTPS traffic. If --client-ca-file argument is set, any request presenting a client certificate signed by one of the authorities in the client-ca-file is authenticated with an identity corresponding to the CommonName of the client certificate.

Impact

TLS and client certificate authentication must be configured for your Kubernetes cluster deployment.

Audit

Run the following command on the Control Plane node:

ps -ef | grep kube-apiserver

Verify that the --client-ca-file argument exists and it is set as appropriate.

Remediation

Follow the Kubernetes documentation and set up the TLS connection on the apiserver. Then, edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml on the master node and set the client certificate authority file.

--client-ca-file=<path/to/client-ca-file>

Default Value

By default, --client-ca-file argument is not set.

References

1. https://kubernetes.io/docs/reference/command-line-tools-reference/kube-apiserver/
2. https://github.com/kelseyhightower/docker-kubernetes-tls-guide

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	3.10 Encrypt Sensitive Data in Transit		*	*
v7	14.4 Encrypt All Sensitive Information in Transit		*	*